He also ate a doughnut. This occurred right at the start, after Mr. Letterman had noted that viewers might never have expected the Garden State governor to show up on the “Late Show” couch due to all the Christie weight jokes they’ve told on the program.

Letterman was going on about how he was sorry if he’d given offense, and how Governor Christie was a regular guy for showing up, when the latter reached into his pocket and pulled out the pastry. It was a real doughnut, too – sugar-coated and jelly-filled. No carrot muffins for him.

Christie then went on to explain that he only cared if Letterman was funny, and that he found, oh, about 40 percent of the Christie weight cracks to be comedic.

He read two of his favorites.

“Celebrity birthday today. Chris Christie turned 50. He blew out the candles on his cake – and wished for another cake,” said the governor, giggling along.

Then he added, “A billion dollars will be spent on potato chips on Super Bowl Sunday. And that’s just at Governor Christie’s house.”

So why the magnanimity? After all, Letterman has been pretty brutal on Christie over the years. And Christie’s got a temper – look at the way he blasted his own Republican Party when House Speaker John Boehner held up a vote on aid for hurricane Sandy victims in January.

We’d say Christie accomplished a number of things with his appearance. First, he defused the weight issue, to some extent. He’s going to continue to be asked about that as his political career goes forward, and joking about it in front of a national audience can only help his image.

Third, and most immediately, he’s got a burst of good publicity for his gubernatorial campaign, while spreading the word that New Jersey still has problems in its recovery from hurricane Sandy and needs continued aid and effort from folks outside the state.

“We still have 42,000 families tonight who are homeless,” said New Jersey’s chief executive.

Will he run for president in 2016? Letterman asked, and Christie, as he always does, made clear that he might, depending on what US politics looks like in a few years. Given his performance on the show, he certainly continues to look like a viable candidate.

But the last point we’ll make is that the Letterman appearance also highlights the biggest obstacle standing in the way of a Christie White House bid. That’s the national Republican Party. Christie’s a Northeastern moderate, and he doesn’t hide the fact that he’s got conflicts with those in the GOP who held up Sandy aid, in part because some in the party are leery of federal disaster spending.

“When it happens in their backyard, it needs to be taken care of, but if it's somewhere else it isn’t as important,” he told Letterman.

And he took a parting shot at Speaker Boehner, by name, for delaying the aid vote. “I made my views known to him, and I was less gentle privately than I was publicly,” said Christie.

Christie appears to have made up with Letterman. If he wants to run for president, he’ll have to do the same thing with the current speaker of the House and GOP fiscal conservatives.